The subject is too big for me.
It would be like "Music - post your favorites".
I prefer foreign films to American ones. Italian, French, British, German, Scandinavian, etc.
A couple off the top of my head:
The Simple-Minded Murder
http://www.imdb.com/title/tt0083888/
One Deadly Summer
http://www.imdb.com/title/tt0086655/
The seven Samurais
Kurosawa, Ettore Scola, Taviani-brothers, The best Sergio Leone flicks, etc, etc.